Stump injections with soil fumigants to eradicate Armillariella mellea from young-growth ponderosa pine killed by root rot.
Five fumigants were tested by injection into soil, into stumps or both, in plots within typical A. mellea disease centres in an area in Washington where Pinus ponderosa is the main tree species. Isolations from stumps excavated 1 yr after treatment showed that methyl bromide, chloropicrin and Vorlex eradicated A. mellea, while carbon disulphide and metham-Na were nearly as effective. The 3 application methods were equally effective. The fungal antagonist Trichoderma sp. was unaffected by the fumigants except methyl bromide which resulted in a significant increase in Trichoderma.<new para>ADDITIONAL ABSTRACT:<new para>The root rot creates unproductive disease centres in young-growth Pinus ponderosa after removal of the old growth timber. The pathogen persists in stumps in the centres, keeping the land indefinitely unproductive. It was effectively eradicated from infected stumps by in situ fumigation with methyl bromide, Vorlex [methyl isothiocyanate], chloropicrin, carbon disulphide and Vapam [metham-sodium]. Trichoderma appeared to be unaffected by the fumigants, except for methyl bromide which resulted in a significant increase in its incidence.